The invention relates generally to a recuperated microturbine system for use in power generation, and more specifically to a housing construction for the recuperator core of the microturbine system. The recuperator uses hot exhaust gases from a power turbine to heat compressed air prior to the compressed air being mixed with fuel and being burned in a combustor. Preheating the compressed air increases the efficiency of the microturbine system.
During operation, the recuperator core is exposed to large temperature excursions which cause the recuperator core to grow and shrink. One problem associated with microturbine systems is how to accommodate and selectively restrict the thermal growth of the recuperator core.
The present invention provides a recuperated microturbine engine including a recuperator core, a compressor, a turbine, a combustor, a generator, and a recuperator housing. The recuperator core includes at least one compressed air flow region and at least one exhaust gas flow region. The compressor provides compressed air to the compressed air flow region, and the turbine provides hot exhaust gas to the exhaust gas flow region to heat the compressed air in the compressed air flow region. The combustor receives the heated compressed air from the compressed air flow region, and burns the preheated compressed air with fuel to create products of combustion. The turbine communicates with the combustor and operates in response to expansion of the products of combustion. The hot exhaust gas provided by the turbine includes spent products of combustion. The generator is driven by the turbine to generate electricity.
The recuperator housing substantially encloses the recuperator core, and is intimate with the recuperator core such that the recuperator housing assumes substantially the same temperature as the recuperator core. The recuperator housing is constructed of material having substantially the same coefficient of thermal expansion and thickness as that of the recuperator core to permit the housing to thermally expand and contract at substantially the same rate as the recuperator core.
Preferably, the at least one compressed air flow region includes a plurality of compressed air flow regions defined by heat exchange cells, and the at least one exhaust gas flow region includes a plurality of exhaust gas flow regions defined between the cells. The recuperator core also preferably includes an inlet manifold communicating between the compressor and the cells, and an outlet manifold communicating between the cells and the combustor.
The recuperator housing may include manifold wrap portions, side portions, inlet and exhaust plenum portions, and top and bottom sheets. The manifold wrap portions cover the outer surfaces of the inlet and outlet manifolds of the recuperator core. The side portions frame the sides of the recuperator core around the inlets and outlets of the exhaust gas flow regions. The inlet and exhaust plenum portions are supported by the side portions. The inlet plenum portion communicates between the turbine and the inlets of the exhaust gas flow regions, and the exhaust plenum portion communicates between the outlets of the exhaust gas flow regions and a microturbine system exhaust duct. The top and bottom sheets cover the top and bottom, respectively, of the recuperator core, and are secured to the respective top and bottom edges of the side portions. The top and bottom sheets may be metallurgically bonded to the inlet and outlet manifolds of the recuperator core.
The side portions may be made integrally with the manifold wrap portions and plenum portions such that the recuperator housing includes only two side pieces that are joined at only two seams around the sides of the recuperator core. The top and bottom sheets are then fastened to the top and bottom edges of those two side pieces. Alternatively, any one or more of the side portions, manifold wrap portions, and plenum portions can be made separately from the other portions, such that the portions are fastened together around the recuperator core at more than two seams.
An exoskeleton or superstructure may be provided around the recuperator core and outside of the recuperator housing. The superstructure may include top and bottom plates above the top sheet and below the bottom sheet, respectively. Tie rods may be interconnected between the top and bottom plates outside of and spaced from the recuperator housing. Because the tie rods are outside of the recuperator housing, the tie rods are not exposed to the same heat cycles as the recuperator core and the intimate recuperator housing. Additionally, the tie rods may be manufactured of material having a lower coefficient of thermal expansion than that of the recuperator core and housing. The superstructure therefore restricts expansion of the recuperator core and housing in the stackwise direction.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.